Topic: Just scored Unobtanium - Marlin Crawler Rebuilt R151F and T-Case

[bigwill837]

Last week I went to look at a 1985 Pickup for sale local to me. Seller mentioned he had a Marlin Crawler rebuilt replacement transmission "for a Supra". After a little poking around, I realized it was a Marlin Crawler R151F transmission and forward-shift transfer case. I was able to negotiate a fair deal, and the trans and t-case is now in my garage! Score!

I think the trans has the 3.83:1 1st gear and the forward shift t-case has stock 2.28:1 gears.







I'd like to run a dual transfer case in my project truck. My question is, what's the most efficient/economical way to build a dual case with what I have? I've read that it's best to run the 2.28:1 gears in the Crawl Box and run the 4.7:1 gears in the t-case. Plus my forward shift case needs to be in the Crawl Box, not the Transfer Case.

Should I just buy another RF1A top-shift core, 4.7:1 gears, MC08 adapter, and two rebuild kits? Then take apart my current T-case and convert it to a forward shift Crawl Box? And convert the core to a 4.7:1 top-shift t-case?

Or can I run 4.7:1 gears in the Crawl Box and 2.28:1 gears in the t-case since the R151F output is 23 spline? Then I would just need to convert the t-case to top shift instead of forward shift (and source a forward shift Crawl Box core)?

Or is it easier to just sell the rebuilt Marlin t-case and start from scratch?

[KDNICKELS]

Personally, I would go with option A: Use the one you have now for your crawl box since it already has the factory 2.28 gears and its forward shift. I would then source a top shift case for your rear case, install 4.7 gears into it, and purchase an MC08 dual case adapter plate to mate them together. I would not run 4.7 gears in the crawl box. I hope this helps!

[bigwill837 [OP]]

Personally, I would go with option A: Use the one you have now for your crawl box since it already has the factory 2.28 gears and its forward shift. I would then source a top shift case for your rear case, install 4.7 gears into it, and purchase an MC08 dual case adapter plate to mate them together. I would not run 4.7 gears in the crawl box. I hope this helps!

Thanks so much! I just spoke to James at Marlin Crawler on the phone, and he recommended the same thing!

Now just need to get those 23-spline MC08s back in stock!

Thanks again.

[Cheesemaker]

I love my R151F!!  But remember, the first 2 gears are lower.  Not just the first gear.  The second isn't as much of a difference, but it still is.

[bigwill837 [OP]]

I love my R151F!!  But remember, the first 2 gears are lower.  Not just the first gear.  The second isn't as much of a difference, but it still is.

Thanks, I didn't realize that about the 2nd gear. I'm 99% sure the Seller bought it from Marlin with the optional 3.83 1st gear.


...Now I just need to find a 1979 to 1985 Pickup to put it into 

[Cheesemaker]

Thanks, I didn't realize that about the 2nd gear. I'm 99% sure the Seller bought it from Marlin with the optional 3.83 1st gear.


...Now I just need to find a 1979 to 1985 Pickup to put it into 

I love to launch off the line at a light, but it climbs the rpm range fast before having to grab second.